A magnetic bearing apparatus supports a rotational shaft in a contactless fashion through magnetic levitation by using a magnetic force generated by flowing an electric current to an electromagnet. In the magnetic bearing apparatus, when the balance of the rotational shaft is not good, the whirling of the rotational shaft is increased, and a large controlling reaction force against an electromagnetic vibration force is applied to a stator. This results in fears that vibration caused by the controlling reaction force affects badly equipment which utilizes the rotation of the rotational shaft. For example, when a magnetic bearing apparatus is used in a turbo molecular pump which is disposed on the periphery of an apparatus such as an exposure apparatus or an electron microscope which is apt to be badly affected by vibration, there are fears that vibration caused by the magnetic bearing apparatus is transmitted to the peripheral apparatus via a stator or a fixed frame. To deal with this situation, the technologies of correcting the imbalance of the rotational shaft have been developed (for example, JPH6-193631A).
However, it is difficult to eliminate the imbalance of the rotational shaft completely, and in reality, the imbalance of the rotational shaft is permitted to some extent. Because of this, it is difficult to prevent completely the vibration caused by the magnetic bearing apparatus from being transmitted to a constituent component of a apparatus which is situated within an influential range of the magnetic bearing apparatus such as, for example, a casing of the magnetic bearing apparatus and an apparatus on the periphery of the magnetic bearing apparatus (for example, the exposure apparatus or the electron microscope which is described above). Moreover, vibration which does not constitute a problem when the rotational shaft rotates at low speeds sometimes constitutes a problem when the rotational shaft rotates at high speeds. On the contrary, vibration which does not constitute a problem when the rotational shaft rotates at high speeds sometimes constitutes a problem when the rotational shaft rotates at low speeds. The transmission properties of vibration to the constituent component within the influential range depend upon how the constituent component is connected or supported, and therefore, it is difficult to predict, at a specific location where vibration is caused, a magnitude of vibration caused in the constituent component which is situated within the influential range of the magnetic bearing apparatus. When the rotational shaft is balanced mechanically, normally a weight is attached to a balancing plane which is provided on the rotational shaft or the balancing plane is cut by a drill or the like. However, when only a narrow space is available, when it is difficult to expose the correcting surface due to corrosion or the like, or when a person cannot touch the balancing plane due to the polluted environment or the like, it is difficult to balance the rotational shaft mechanically.